The present invention relates to liquid fuel lamps, including lamps suitable for use in outdoor garden torches.
Liquid fuel torches or lights are available in the form of pseudo candles that are designed primarily for outside use. One such liquid fuel light is described in U.S. Pat. No. 2,512,885.
There are also a variety of known garden torches that are designed to be employed out-of-doors in hotel gardens, residential patios, or the like. These torches typically have a fuel container in which is placed a wick. The wick extends upwardly through and is held by a flame guard. The flame guard extends over and protects the fuel container from the flame. Typically a threaded cap is attached to the under side of the flame guard, the cap receiving and closing the fuel container and securing it to the flame guard. These torches also often employ a basket made of bamboo or other materials. The basket is of a size and shape such as to conveniently hold the fuel container in a generally upright position, and the basket itself is often held aloft by a ground-engaging pole. Often the flame guard extends laterally sufficiently to cover the upper rim of the basket, providing both a decorative effect and protecting the basket from the flame.
There are various problems with many of the flame guard and cap systems used to separate the flame from the fuel container and to close the fuel container. The flame guard itself directly contacts the wick at the point where it is burning and therefore is typically made of metal so as to withstand flame temperatures. The common use of inexpensive, ferrous metals in flame guards leads to potential rusting problems. But, even more problematic, metal conducts heat. Typically, the fuel container of liquid fuel torches can become distinctly warm and must be vented to relieve internal pressure caused by heat transferred via the flame guard from the torch's flame to the fuel container. Such heat also makes the use of a plastic fuel container difficult, as opposed to traditional metal containers, because of the danger of melting or deforming a plastic container.
A garden torch sold by Lamplight Farms, Inc. of Menomonee Falls, Wis., appears to be designed to address the issue of heat transfer to the fuel container. Apparently at least in part to reduce such heat transfer, the wick of the Lamplight Farms torch is held by a vertically oriented, metal sleeve that forms a part of a metal flame guard. The metal sleeve extends through the flame guard and ends at a point under the flame guard. Then, after an air gap, a metal screw cap is located beneath the metal sleeve. The screw cap has a central hole that has the same diameter as and is held in line with the metal sleeve. The fuel container screws into the screw cap. The wick extends downwardly through the metal sleeve and then on downwardly, through the hole in the screw cap and into the fuel container. Four, spaced braces fasten the screw cap to the underside of the flame guard, the braces attaching to the flame guard at a point remote from the flame.
As a consequence of this structure, the metal heat-flow path from the flame's location to the fuel container is made considerably longer and more circuitous than would be the case if the metal sleeve attached directly to the cap or if the cap were fastened directly to the flame guard, without the use of the intervening braces. Furthermore, the braces have relatively small cross sections, further reducing heat flow toward the fuel container. However, the resulting structure is complex and involves a number of parts that must be formed separately and then assembled, leading to manufacturing expense.
Presenting a further disadvantage, in the Lamplight Farms torch, the part of the wick that spans the air gap between the metal sleeve and the screw cap is openly exposed to the surrounding atmosphere. This exposure is in a space located directly under the metal flame guard, and, as a consequence, the air in that space predictably warms as the torch burns. Because that space is open to the atmosphere, it requires no separate venting to avoid pressure build-up. However, this arrangement leaves exposed to warmed air a portion of wick that is wet with fuel and provides no structure capable of blocking air circulation around the wet wick from even a slight breeze or other air flow. The fuel thus warmed may be expected to evaporate from the exposed wick and escape unburned into the atmosphere, causing waste and increased raw fuel odors. Because the amount of fuel evaporated could be expected to vary with the amount of breeze blowing on the lamp, a further result would be inconsistent overall fuel consumption rates.
The Lamplight Farms torch just described is sold equipped with a plastic fuel container. Even though fuel container venting would appear still to be necessary, the structures just described for reducing heat flow apparently are sufficiently successful that the fuel container can be made of a meltable plastic rather than metal. However, as mentioned above, the torch is deficient in that it requires manufacture by assembly of complicated, multi-component substructures, leading to a cost of manufacture higher than that which would be required for a simpler structure, and in that it allows raw fuel to evaporate from an exposed portion of fuel-wet wick.
Typical prior art torches, including the Lamplight Farms torch, use fuel containers that have narrow, restricted necks. This feature makes it undesirably difficult for a manufacturer to insert the wick into the fuel container in an automated assembly process and also makes it difficult for a user to attach a fuel container to the cap held by a flame guard, whether refilling or replacing an exhausted fuel container. It may even be necessary for a user to guide the fuel-wetted wick by hand into the neck of such a fuel container, which may be messy and distasteful. The need to insert a wick through first the metal tube and then the hole in the screw cap makes the Lamplight Farms torch especially difficult to manufacture.
It can therefore be seen that there is a need for improved liquid fuel lamps, including such lamps suitable for use in garden torches.